From what I've been able to gather on the internet, it's a song that can be accompanied by a game with small children ("Mit den zehn Fingern spielen, was der Text aussagt. Kann man auch mit Kindern in der Kindergruppe spielen, z.B. zehn (oder acht oder drei) kleine Zappelkinder.") But what exactly does the verb "zappeln" mean and is there any reasonable English translation of "Zappelfinger"? I looked up "zappeln" at my usual internet dictionary (Beolingus) and got "flounce, flounder, fidget" but that only helped a little. "Fidget fingers"?

Zappeln means to move your body or a part of your body to and fro. The definition of flounce and flounder are completely different . Fidget would fit in another context (boring, nervous). In this case I'd go with wiggle as teylyn suggests, or wriggle.
–
Em1May 23 '13 at 7:21